linux-kernel - Re: [PATCH] x86: fix PAE pmd

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Message-ID: <20080506202201.GB12654@escobedo.amd.com>
Date:	Tue, 6 May 2008 22:22:01 +0200
From:	Hans Rosenfeld <hans.rosenfeld@....com>
To:	Hugh Dickins <hugh@...itas.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Jeff Chua <jeff.chua.linux@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Gabriel C <nix.or.die@...glemail.com>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	Nishanth Aravamudan <nacc@...ibm.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH] x86: fix PAE pmd_bad bootup warning

On Tue, May 06, 2008 at 08:49:23PM +0100, Hugh Dickins wrote:
> So Hans' original hugepage leak remains unexplained and unfixed.
> Hans, did you find that hugepage leak with a standard kernel, or were
> you perhaps trying out some hugepage-using patch of your own, without
> marking the vma VM_HUGETLB?  Or were you expecting the hugetlbfs file
> to truncate itself once all mmappers had gone?  If the standard kernel
> leaks hugepages, I'm surprised the hugetlb guys don't know about it.

I used a standard kernel (well, not quite, I had made some changes to
the /proc/pid/pagemap code, but nothing that would affect the hugepage
stuff) and some simple test program that would just mmap a hugepage.

I expected that any hugepage that a process had mmapped would
automatically be returned to the system when the process exits. That was
not the case, the process exited and the hugepage was lost (unless I
changed the program to explicitly munmap the hugepage before exiting).
Removing the hugetlbfs file containing the hugepage also didn't free the
page.


-- 
%SYSTEM-F-ANARCHISM, The operating system has been overthrown

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